The present invention relates to a solid electrolytic capacitor using a solid electrolyte.
Recently, as electronic equipment has been reduced in size and weight, high-frequency capacitors with a smaller size and a larger capacity have been required. As such capacitors, a solid electrolytic capacitor has been proposed, which includes a dielectric layer formed by anodizing a surface of an anode made of a sintered body of a valve metal such as tantalum, niobium, titanium or aluminum, and a solid electrolyte layer provided on the dielectric layer. For the solid electrolyte layer, an electroconductive polymer is used so as to reduce equivalent series resistance (ESR).
However, a dielectric layer formed by anodizing a surface of an anode made of a valve metal or the like has a problem that an insulating property is deteriorated in a defective portion such as a crack and a thin portion in the dielectric layer, which is generated at the time of formation, and leakage current is increased.
In order to solve the above-mentioned problem, Japanese Patent Application Unexamined Publication No. 2001-167981 proposes a technique for reducing leakage current by forming a solid electrolyte layer made of an electroconductive polymer with the use of an iron-based oxidizer and then washing the solid electrolyte layer with a washing solution including, for example, citric acid for reducing the concentration of residual iron ions in the solid electrolyte layer.
However, the method described in Japanese Patent Application Unexamined Publication No. 2001-167981 requires washing a solid electrolyte layer with a washing solution including, for example, citric acid, which makes a manufacturing process complicated.